SCIENTIFIC MISCELLANY.

Otago Witness, Issue 3673, 5 August 1924, Page 69

SCIENTIFIC MISCELLANY.

(For the Witness.) A BIG SILVER “NUGGET.” A mass of silver ore, 2® by 24 by 40 inches in size, is the contribution of the Frontier Mine of Canada to the British Empire Exhibition. It weighs tons, and, assaying 12,000 ounces to the ton, is estimated to contain over 30,000 ounces of silver. CORNS AS WEATHER INDICATORS. Corns may give weather warnings, as is so often affirmed, the explanation being that the leather of the shoes swells and shrinks as the moisture in the air varies, and the foot is very sensative to the changes. In a recent American Chemical Society paper, J. A. Wilson showed that different kinds of leather give very different degrees of pinching. SULPHUR HARDENED STONE. Sandstone normally resists a compression of 8000 to 9000 pounds per square inch, but filling its pores by immersion in molten sulphur for several hours has given the U. S. Bureau of Standards a stone having a strength of 30,000 pounds, though of a durability as yet unknown. Other porous materials, such as cement, are greatly strengthened by the sulphur bath. TESTING PLANTS. The Botanic Gardens of Harvard University, founded in 180 1 and covering 7 acres, is to be made a testing ground for all hardy herbs suitable for culture in the north-eastern United States, with such greenhouse materials as it can accommodate ; and it expects to have all materials of American nursery catalogues in cultivation within a year, except the hardy woody shrubs. The present collection of some 2000 species will be increased to at least 6000, while 1000 annuals will be grown. A NEW RAILWAY LIGHT. An acetylene fog signal, designed for use on railway lines where electric service is not available, consists of a castiron standard, with a lantern on top, and a cylinder of acetylene dissolved in acetone in the base. A pilot light burns permanently, a flashing mechanism working automatically when the gas is turned on. With approach of fog the signalman switches on the flasher, and the lantern sends out 200 flashes a minute of the same colour as the permanent signal, thus warning the engineer when the stationary light would not be seen. One acetylene charge lasts three to six months. POROUS CONCRETE. The light-weight concrete of Axel Eriksson, Swedish architect, is made of cement and shale lime, with a little added aluminum or zinc powder. Water in contact with the mixture generates hydrogen, and the mortar sets while in a porous condition from the contained gas. Mortar of 30 parts of cement to 60 of lime, with a porosity of 75 per cent, hardens into concrete weighing 40 to 50 pounds per cubic foot. The concrete after a few weeks has a compressive strength of 350 to 400 pounds per square inch, it resists fire and weathering, and in walls 6 or 8 inches thick is recommended for dwellings of one and two stories. It is not, however, suitable for chimneys. SUNSHINE AND MORTALITY. The prevalent idea that we cannot have too much sunshine for health is challenged by W. H„ Dines, F.R.S., who points out in Nature that many wellknown statistical facts are opposed to this belief. In European countries the deathrate is highest in the south and lowest

in the north, and the British Isles and the Scandinavian countries are especially favoured. Though tile duration of possible sunshine is nearly the same in both parts, the intensity is far greater in the south. English records for 1881 to 1912 being at hand, comparison was made of the summer sunshine and summer deathrate of the different years, and this showed that the four most sunless summers (1888, 1897, 1910 and 1912) all had an exceptionally low death-rate, while the sunniest summers (1877, 1899 and 1911) had more than the ■ average number of deaths. It is contended that the fact ihat ultra-violet rays are helpful in certain diseases does not prove that an excess of sunlight is generally beneficial. It is thought to be hardly credible that sunlight alone should be prejudicial to health, and the explanation is suggested ..that it is the heat, with which sunshine is usually associated, that is harmful. EYE ACCIDENTS. Of a total of 100,000 totally blind persons in the United States, " 15,000 owe their condition to industrial accidents, while a still greater number suffer from loss of one eye, or impaired vision, caused by accidents while at work. Lewis H. Carris, referring to the inquiry by the National Committee for the Prevention of the Blind, states that approximately 200,000 eye accidents occur annually, and that there is hardly an industrial occupation in America that does not add yearly to the blind and near blind. The chief eye hazards belong in three classes. First, we have accidents from flying ‘fragments of metals, minerals and wood, from splashing liquids, such as molten metals and harmful chemicals, and from explosions ; then there are infections and diseases that arise from neglect of eye injuries, incompetent first-aid treatment, contact with contagious diseases, and exposure to excessive radiated heat; and, finally, there is eyestrain, resulting from poor lighting improper placing when at work; and neglect of defective vision. Means for improvement include safety legislation, safety education, and, not least, carefully organised preventive measures in the individual plant. Various establishments have undertaken to better conditions, and with mechanical guards, frequent inspections, and efficient poster and other warnings, have practically banished eye accidents. HORMONES AND NERVES. A class of recently recognised body substances called hormones has aroused much interest on account of their profound influence on growth, child health, and diabetes. Their action, suggests a writer in the English Mechanic, may be defined as supplementary to that of the nervous mechanism in regulation of the bodily functions, but, unlike the general nervous control throughout the body, the hormone control is confined to only a few organs. In general, the organs responding quickly to external stimulus are subject to nervous control, while those of slower action are under hormone control. An instance of do»ble control is the secretion of digestive juices, the initial flow resulting from nervous impulses of the mouth organs of taste, and the continued flow being due to the hormone liberated by the presence of food in the stomach. These facts have a bearing on our choice of foods. The digestive flow being due to f ratification of appetite, digestion is acilitated with appetizing food, and it is found that meat or meat juice is most effective in liberating the flow-stimulating hormone. Here is physiological justification for beginning a meal with soup. The pancreatic secretion, so important in indigestion, is, like that of the gastric glands, controlled by a hormone set free by presence of food. Besides the external secretion of the pancreas, there is an internal secretion into the blood having a very definite function in utilizing body sugar. Losing the pancreas, animals develop symptoms of diabetes, and pancreas disease in man is followed by diabetes. Extraction of the hormone controlling the pancreas secretion has been at last made possible, the sugar of the blood being brought under control. Several other organs produce an internal secretion, some secretions affecting only a certain part, but the thyroid gland hormone has a general influence on growth, its early absence giving cretinism.